Analysis of 32 common susceptibility genetic variants and their combined effect in predicting risk of Type 2 diabetes and related traits in Indians.

AIMS: Recent genome-wide association studies have identified several Type 2 diabetes-related loci. We investigated the effect of susceptibility genetic variants, individually, together and in combination with conventional risk factors, on Type 2 diabetes and diabetes-related traits in Indians. METHODS: We genotyped 33 variants in 1808 Indian patients and 1549 control subjects and performed association analyses with Type 2 diabetes and related traits using an additive model for individual variant and for genetic risk score based on 32 polymorphisms. The discriminatory value of genetic risk over conventional risk factors was analysed using receiver-operating characteristics curve analysis. RESULTS: The allelic odds ratio ranged from 1.01 (95% CI 0.85-1.19) to 1.66 (95% CI 1.32-2.01) for single-variant analyses. Although, only 16 variants had significant odds ratios, the direction of association for others was similar to earlier reports. The odds ratio for Type 2 diabetes at each genetic risk score point was 1.11 (95% CI 1.09-1.14; P = 5.6 × 10(-17)) and individuals with extremes of genetic risk score (≥ 29.0 and ≤ 17.0) had a 7.5-fold difference in risk of Type 2 diabetes. The discrimination rate between control subjects and patients improved marginally on addition of genetic risk score to conventional risk factors (area under curve = 0.959 and 0.963, respectively; P = 0.001). Of all the quantitative traits analysed, MC4R variants showed strong association with BMI (P = 4.1 × 10(-4)), fat mass per cent (P = 2.4 × 10(-4)) and other obesity-related traits, including waist circumference and hip circumference (P = 2.0 × 10(-3) for both), as well as insulin resistance (P =0.02). CONCLUSIONS: We replicated the association of well-established common variants with Type 2 diabetes in Indians and observed a similar association as reported in Western populations. Combined analysis of 32 variants aids identification of subgroups at increased risk of Type 2 diabetes, but adds only a minor advantage over conventional risk factors.

Association of genetic variation in FTO with risk of obesity and type 2 diabetes with data from 96,551 East and South Asians.

AIMS/HYPOTHESIS: FTO harbours the strongest known obesity-susceptibility locus in Europeans. While there is growing evidence for a role for FTO in obesity risk in Asians, its association with type 2 diabetes, independently of BMI, remains inconsistent. To test whether there is an association of the FTO locus with obesity and type 2 diabetes, we conducted a meta-analysis of 32 populations including 96,551 East and South Asians. METHODS: All studies published on the association between FTO-rs9939609 (or proxy [r (2) > 0.98]) and BMI, obesity or type 2 diabetes in East or South Asians were invited. Each study group analysed their data according to a standardised analysis plan. Association with type 2 diabetes was also adjusted for BMI. Random-effects meta-analyses were performed to pool all effect sizes. RESULTS: The FTO-rs9939609 minor allele increased risk of obesity by 1.25-fold/allele (p = 9.0 × 10(-19)), overweight by 1.13-fold/allele (p = 1.0 × 10(-11)) and type 2 diabetes by 1.15-fold/allele (p = 5.5 × 10(-8)). The association with type 2 diabetes was attenuated after adjustment for BMI (OR 1.10-fold/allele, p = 6.6 × 10(-5)). The FTO-rs9939609 minor allele increased BMI by 0.26 kg/m(2) per allele (p = 2.8 × 10(-17)), WHR by 0.003/allele (p = 1.2 × 10(-6)), and body fat percentage by 0.31%/allele (p = 0.0005). Associations were similar using dominant models. While the minor allele is less common in East Asians (12-20%) than South Asians (30-33%), the effect of FTO variation on obesity-related traits and type 2 diabetes was similar in the two populations. CONCLUSIONS/INTERPRETATION: FTO is associated with increased risk of obesity and type 2 diabetes, with effect sizes similar in East and South Asians and similar to those observed in Europeans. Furthermore, FTO is also associated with type 2 diabetes independently of BMI.

Effect of physiological doses of oral vitamin B12 on plasma homocysteine: a randomized, placebo-controlled, double-blind trial in India.

BACKGROUND/OBJECTIVES: Vitamin B(12) (B(12)) deficiency is common in Indians and a major contributor to hyperhomocysteinemia, which may influence fetal growth, risk of type II diabetes and cardiovascular disease. The purpose of this paper was to study the effect of physiological doses of B(12) and folic acid on plasma total homocysteine (tHcy) concentration. SUBJECTS/METHODS: A cluster randomized, placebo-controlled, double-blind, 2 x 3 factorial trial, using the family as the randomization unit. B(12) was given as 2 or 10 microg capsules, with or without 200 microg folic acid, forming six groups (B(0)F(0), B(2)F(0), B(10)F(0), B(0)F(200), B(2)F(200) and B(10)F(200)). Plasma tHcy concentration was measured before and after 4 and 12 months of supplementation. RESULTS: From 119 families in the Pune Maternal Nutrition Study, 300 individuals were randomized. There was no interaction between B(12) and folic acid (P=0.14) in relation to tHcy concentration change and their effects were analyzed separately: B(0) vs. B(2) vs. B(10); and F(0) vs. F(200). At 12 months, tHcy concentration reduced by a mean 5.9 (95% CI: -7.8, -4.1) micromol/l in B(2), and by 7.1 (95% CI: -8.9, -5.4) micromol/l in B(10), compared to nonsignificant rise of 1.2 (95% CI: -0.5, 2.9) micromol/l in B(0). B(2) and B(10) did not differ significantly. In F(200), tHcy concentration decreased by 4.8 (95% CI: -6.3, -3.3) micromol/l compared to 2.8 (95% CI: -4.3, -1.2) micromol/l in F(0). CONCLUSION: Daily oral supplementation with physiological doses of B(12) is an effective community intervention to reduce tHcy. Folic acid (200 microg per day) showed no additional benefit, neither had any unfavorable effects.

Adiposity, inflammation and hyperglycaemia in rural and urban Indian men: Coronary Risk of Insulin Sensitivity in Indian Subjects (CRISIS) Study.

AIMS/HYPOTHESIS: The aim of this study was to investigate whether the higher prevalence of insulin resistance and glucose intolerance in urban compared with rural Indian men is related to their higher adiposity (percentage body fat) and the associated inflammatory state. METHODS: We studied 149 rural, 142 urban slum and 150 urban middle-class male residents (age 30-50 years), who were selected by stratified random sampling. We measured body fat (bioimpedance), waist circumference, glucose tolerance (75 g OGTT), insulin resistance [homeostasis model assessment (HOMA-IR)], beta cell function (insulinogenic index) and inflammatory markers (total leucocyte count, IL-6, TNF-alpha and C-reactive protein). RESULTS: Adiposity, waist circumference, HOMA-IR, insulinogenic index and both fasting and 120 min plasma glucose concentrations increased progressively from rural through to urban slum and urban middle-class men. Inflammatory markers were higher in urban than in rural men. Adiposity was strongly related to HOMA-IR (r = 0.57, p < 0.001) and to insulinogenic index and glycaemic parameters (r = 0.25, p < 0.001 for both). Adiposity explained approximately two thirds of the difference in HOMA-IR between the urban middle-class men and the rural and slum residents, but its contribution to the difference in insulinogenic index and 120 min plasma glucose concentration was not significant. Inclusion of C-reactive protein, IL-6 and total leucocyte count in the models did not further explain these results, nor did the inclusion of waist circumference. There was a significant residual difference after these adjustments. CONCLUSIONS/INTERPRETATION: Adiposity is a major contributor to the difference in insulin resistance between rural and urban Indian men; there was no additional contribution from inflammation or central obesity. Other unmeasured factors also seem to contribute to the metabolic differences between rural and urban men.

Vitamin B12 and folate concentrations during pregnancy and insulin resistance in the offspring: the Pune Maternal Nutrition Study.

AIMS/HYPOTHESIS: Raised maternal plasma total homocysteine (tHcy) concentrations predict small size at birth, which is a risk factor for type 2 diabetes mellitus. We studied the association between maternal vitamin B12, folate and tHcy status during pregnancy, and offspring adiposity and insulin resistance at 6 years. METHODS: In the Pune Maternal Nutrition Study we studied 700 consecutive eligible pregnant women in six villages. We measured maternal nutritional intake and circulating concentrations of folate, vitamin B12, tHcy and methylmalonic acid (MMA) at 18 and 28 weeks of gestation. These were correlated with offspring anthropometry, body composition (dual-energy X-ray absorptiometry scan) and insulin resistance (homeostatic model assessment of insulin resistance [HOMA-R]) at 6 years. RESULTS: Two-thirds of mothers had low vitamin B12 (<150 pmol/l), 90% had high MMA (>0.26 micromol/l) and 30% had raised tHcy concentrations (>10 micromol/l); only one had a low erythrocyte folate concentration. Although short and thin (BMI), the 6-year-old children were relatively adipose compared with the UK standards (skinfold thicknesses). Higher maternal erythrocyte folate concentrations at 28 weeks predicted higher offspring adiposity and higher HOMA-R (both p < 0.01). Low maternal vitamin B12 (18 weeks; p = 0.03) predicted higher HOMA-R in the children. The offspring of mothers with a combination of high folate and low vitamin B12 concentrations were the most insulin resistant. CONCLUSIONS/INTERPRETATION: Low maternal vitamin B12 and high folate status may contribute to the epidemic of adiposity and type 2 diabetes in India.

Newborn size, infant and childhood growth, and body composition and cardiovascular disease risk factors at the age of 6 years: the Pune Maternal Nutrition Study.

OBJECTIVE: To study associations of size and body proportions at birth, and growth during infancy and childhood, to body composition and cardiovascular disease (CVD) risk factors at the age of 6 years. DESIGN: The Pune Maternal Nutrition Study, a prospective population-based study of maternal nutrition and CVD risk in rural Indian children. METHODS: Body composition and CVD risk factors measured in 698 children at 6 years were related to body proportions and growth from birth. MEASUREMENTS: Anthropometry was performed every 6 months from birth. At 6 years, fat and lean mass (dual X-ray absorptiometry) and CVD risk factors (insulin resistance, blood pressure, glucose tolerance, plasma lipids) were measured. RESULTS: Compared with international references (NCHS, WHO) the children were short, light and thin (mean weight <-1.0 s.d. at all ages). Larger size and faster growth in all body measurements from birth to 6 years predicted higher lean and fat mass at 6 years. Weight and height predicted lean mass more strongly than fat mass, mid-upper arm circumference (MUAC) predicted them both approximately equally and skinfolds predicted only fat mass. Neither birthweight nor the 'thin-fat' newborn phenotype, was related to CVD risk factors. Smaller MUAC at 6 months predicted higher insulin resistance (P<0.001) but larger MUAC at 1 year predicted higher systolic blood pressure (P<0.001). After infancy, higher weight, height, MUAC and skinfolds, and faster growth of all these parameters were associated with increased CVD risk factors. CONCLUSIONS: Slower muscle growth in infancy may increase insulin resistance but reduce blood pressure. After infancy larger size and faster growth of all body measurements are associated with a more adverse childhood CVD risk factor profile. These rural Indian children are growing below international 'norms' for body size and studies are required in other populations to determine the generalizability of the findings.

Adiposity and hyperinsulinemia in Indians are present at birth.

We studied body size and cord blood leptin and insulin concentrations in newborn urban Indian (Pune, India) and white Caucasian (London, UK) babies to test the hypothesis that the adiposity and hyperinsulinemia of Indians are present at birth. Indian babies (n = 157) were lighter in weight compared with white Caucasian babies [n = 67; median weight, 2805 g vs. 3475 g, respectively; P < 0.001, adjusted for gestational age and sex; -1.52 SD score; confidence interval (CI), -1.66, -1.42] and had smaller abdominal (-2.39 SD score; CI, -2.52, -2.09), midarm (-1.47 SD score; CI, -1.58, -1.34), and head (-1.23 SD score; CI, -1.42, -1.13) circumferences. However, their skinfolds were relatively preserved: subscapular (central) skinfold (-0.32 SD score; CI, -0.43, -0.20) was better preserved than triceps (peripheral) skinfold (-0.86 SD score; CI, -0.97, -0.75). Cord plasma leptin (median, 6.2 ng/ml Pune and 6.4 ng/ml London) and insulin (median, 34.7 pmol/liter Pune and 20.8 pmol/liter London) concentrations were comparable in the two populations but were higher in Indians when adjusted for birth weight, confirming relative adiposity and hyperinsulinemia of Indian babies. Indian mothers were smaller in all respects, compared with white Caucasian mothers, except subscapular skinfold, which was similar in the two populations. Our results support the intrauterine origin of adiposity, central adiposity, and hyperinsulinemia in Indians. Further research should concentrate on elucidating genetic and environmental influences on fetal growth and body composition. Prevention of insulin resistance syndrome in Indians will need to address regulation of fetal growth in addition to prevention of obesity in later life.

Circulating lipids and cardiovascular risk in newly diagnosed non-insulin-dependent diabetic subjects in India.

Circulating concentrations of total cholesterol, triglycerides, non-esterified fatty acids (NEFA), glycerol, and 3-hydroxybutyrate (3-HB) were measured in 133 subjects with normal glucose tolerance (NGT), 78 with impaired-glucose-tolerance (IGT) and 189 non-insulin dependent (Type 2) diabetic (NIDDM) patients. Plasma cholesterol concentration was similar in the three groups; NGT (4.2 (2.3-7.5) mmol l-1, median (range)), IGT (4.7 (2.7-6.3)) and NIDDM (4.3 (2.3-6.9)). Plasma triglycerides (NGT 0.88 (0.37-2.80), IGT 1.26 (0.43-3.82) and NIDDM 1.38 (0.62-3.91) mmol l-1) and NEFA (NGT 0.81 (0.29-1.58), IGT 1.02 (0.33-1.87) and NIDDM 1.02 (0.48-2.77) mmol l-1) were higher in the two hyperglycaemic groups, but blood 3-HB concentration was similar in the three groups. Plasma cholesterol concentration in these subjects is lower than that reported in white Caucasians in the UK and USA and migrant Indian NIDDM patients in the UK. In NIDDM patients plasma cholesterol concentration was related to age, body mass index (BMI), and plasma glucose concentration while plasma triglyceride concentration was related to plasma NEFA and insulin (IRI) concentration. Evidence of ischaemia on electrocardiography in patients with diabetes was associated with higher age, blood pressure, plasma triglyceride, glucose, and IRI concentrations.